FIGMAC: I spent some time as a Navy Flight Instructor.
You've been given some good advice so far.
Bust your butt. Select what you want, the USMC will assign you to what they need you to fly.
Excel at that during your first tour, whatever the airframe.
You second tour will force you to make some interesting choices that you can then add your "post Marine" career considerations into.
Also, if you do select Ospreys, you will get training in both T-44 (or C-12 if it is still flying in Training Wing 4) and TH-57. Your instrument rating is the most important rating you will earn, in terms of its applicability in civilian world. I think you'll earn it in the T-44/C-12.
You'll need to investigate the equivalency route to other ratings after you
earn your wings.
You'll likely need to pay for a bit out of pocket to get what you need for various civlian tickets, so START SAVING YOUR MONEY NOW.
Best wishes and Semper Fi to you, Lieutenant. You are embarking on a great journey.
I envy you.
LW_50
PS: Looks like VT-35 still flies the C-12.
https://www.cnatra.navy.mil/tw4/pipelines.asp
EDIT: Sent you links via PM.